Manufacture of selenium elements



.Ju y 10,1945! A. J.- WLLE Em 2 379,91

MANUFACTURE OF SELEN IUM ELEMENTS Filed May 1, 1945 IN VEN T 0R5 ATTORNEY iarly placed on the carrier plate as showminjl 'i Patented Jul to; [tins 2.319319 MANUFACTURE or SELENIUM ELEMENTS Arthur J. Miller and Eugene P. Sauerborn,

Newark, N. J., assignors to Federal Telephone &

Radio Corporation, tion of Delaware New York, N. Y., a corpora- Application May 1, 1943, Serial No. 485,383

, 9Claims. J This invention relates to the manufacture of selenium coated elements such as are used for rectifiers and particularly to the simultaneous,

treating and processing of a plurality of such elements. a

The object of this invention is to make or procass a plurality of selenium rectii'lers as a unit during their manufacture.

Selenium elements are commonly made b applying selenium to a base plate posed of a metal as iron, steel or aluminum or the like, andsubjecting the treated plates to ele-;'

vated temperatures in one or more steps and also 'to pressure if desired. A counterelectrode comprising a conducting substance such as Woods ordinarily com bearing the elements is then placed in a press indicated by the press platens and 6 in Fig. 1, so that the burrs are pressed into the carrier plate which should be of a metal soft enough to receive them, such as aluminum. Fig. 3 shows one of the-elements in compression between the press platens and shows the burr pressed into metal is then usually applied, as by' spraying, on

the seleniumsurface. It is thought that the rectiiying property, i. e., the ability to pass current flowing in the forward direction and to block the flow in the reverse direction'is due to the formation .of a "blocking layer at the selenium surface under the counterelectrode.

According to our invention a number of such selenium elements are made as a unit. To do this we provide burrs at the bottoms of the individual base plates so that the burrs may be pressed into a supporting plate which acts as a jig. The various steps in the fabrication and treatment of the elements are carried out with the base plates on the support.

The invention will be better understood by reference to the following detailed description and the attached drawing of which:

Figure 1 is a cross-section view of a selenium coated element shown resting am a carrier plate J18;

Figure 2 is a face view of the element; c Figure 3 shows one of the elements presse into the .118; and

Figure 4 is a face view of a rality of elements afllxed thereto.

Referring to the drawing, Fig: 1 shows across jig having a pluv section. of a rectifier-element in which a circumferential burr I of base plate 4 is resting on the surface of the jig 2. The burr may conveniently be formed by p nching out the base plate by the use of a punch; which by its opera tion produces the hon at oneside of the punched out plate. A selenium coating is then applied; to the surface .of the base plate oppositQthe burr.

.This may conveniently be a. layer of seleni powder. A number "of these elements areisiml 4with their burrs against the jig, and are simithe jig plate. The pressure required is not critical; a pressure of around 4,000 pounds per square inch having been found satisfactory. During the pressing the temperature should be elevated somewhat to soften the selenium for example, in the range of about C. to- C. This may be done by heating the press platens by heating elements 7 andt. The selenium powder is thereby compressed and sintered sufllciently to become a solidthin layer adhering to each base plate. t V

The elements carried by the jig will then ordinarily be subjected to a second heat treatment for example by placing them in an oven at'a temperature in the range of about 150 C. to 217 C., and further treatments may be applied, such as fuming the selenium surfaces by gas or moisture. Followin -this a conducting alloy serving as the counter-electrode is sprayed on the selenium surfaces. Toadapt the elements as rectiflers they are commonly electroformed by passing a D. C. o'r pulsating D. C. current through them in the direction opposite that of normal forward current flow. All of the foregoing steps may be performed while the elements are held in the jig 2; they may then be pushed an a number of base plates, placing the base" plates on a supporting jig with the burrs against the jig, covering the base plates with selenium and pressing the selenium covered plates into the- 6 Jig and then heat treating" applying counterelectrodes and electrofor'ming' the'eiements while The A method of m ki a. plurality of se ing .burrs" at the bottoms of a number of I plates, coverlnsthe tops of. the-base plates with forming burrs mum elements as a unit which comprises for1n selenium and then pressing the selenium covered base plates against a jig so that the burrs enter the jig, and then further treating the elements.

3. The method of making a plurality of selenium elements which comprises punching out base plates with circumferential burrs, placing the base plates with the burrs against the carrier plate, covering the base plates with selenium powder, then pressing the powder covered base plateswith the burrs against the 'jig at an elevated temperature to form adherent solid selenium layers adhering to the base plates and to press the base plates to the jig, and then further treating the elements whilein the jig.

4. Process for making selenium rectifier elements by placing on a jig a plurality of *metal plates each having a burr around the rim so that the burr is touching the ji surface, covering said plates with selenium and subjecting the whole to pressure at an elevated temperature whereby said selenium is sintered to said plates and the burrs forced into the surface of the jig.

5. Process for making selenium rectifier elements by placing on a jig a plurality of metal rim so that the burr is touching the surface of der and subjecting the whole to elevated temperature and pressure whereby said selenium is sintered 'to said plates and the elements held to the jig by the burrs.

7. The combination of a pluralityof selenium rectifier elements and a metal jig plate, said elements each having a punching burr extending substantially entirely around its periphery forced into the surface of said jig.

8. Method of making a plurality of selenium elements by punching out metallic base plates with circumferential burrs, placing said plates on a soft metal jig, covering said plates withjselenium powder, pressing said plates with the burrs against the ji at a temperature in the range C. to C. to sinter the selenium powder to said plates was to form an adherent layer thereon and to' force said burrs into the jig, subjecting the elements to a second heat treatment in the range 150 C. to 217 0., fuming the elements with a gas, spraying a conducting alloy on the selenium surfaces and electroform- ARTHUR J. MILLER. EUGENE P. SAUERBORN, 

